Abstract: A heater system is provided for use with a downdraft range. The heater is constructed and disposed within a burner pan associated with the range to produce a non-uniform heat output relative to the front-to-rear center line of the burner pan. The greater heat output is produced adjacent a side wall of the burner pan which is substantially opposite the air inlet of the proximity ventilation system.

Abstract: A telephony system with automatic test calling. Test access circuitry connected to port circuits enables the test call circuit to select actual ports for a test call and monitor the test call signals. Test calls are initiated either on a periodic basis on in resonse to a fault condition. Any portion of the telephony system therefore can be used in a test call.

Abstract: A fault monitoring and diagnostic system for a telephony switching system. Two call processing systems connect through a programmable switch to port group units that receive individual telephone lines. All signals from the port group units are conveyed to both call processing systems, and the call processing systems operate in synchronism. However, the programmable switch conveys signals back to the port group units from only one of the call processing systems. Fault monitoring and diagnostic circuitry monitors various conditions within the telephony switching system. A test call generator automatically performs test calls thereby to diagnose system problems. If a fault is detected, the fault monitoring and diagnostic system controls the programmable switch and, in appropriate circumstances, couples the output signals from the other call processing system to the port group units. Information concerning the nature of the fault is also provided.